I would like to draw a cross over an image, with a different color for each pixel depending on the background color, so that the cross is always well visible. So I'm trying to change the Composition Mode of the QPainter, but I can't find an acceptable solution.
I have tried QPainter::CompositionMode_Difference, painting with white. This is quite good because it inverts the destination color, but it doesn't work well if the destination color is a middle gray or similar.
The best solution is to get white if the background is "dark" and black if the background is "light". Is there a way to get this effect using only composition modes of the painter?
What about running the Image Composition Example for yourself, and maybe modifying the source/destination images to better fit your scenario? Maybe QPainter::CompositionMode_Xor is what you want?
An alternative solution, which is even very simple, is to use a white cross with a rather thick black outline. In this case you can ensure the visibility of the cross even in case of rather dark or light background images.
Related
The image below has a kind of faded grey look with what seems to be some slight blurring and works quite well as a generic banner image.
Usually I am provided with these images or just find stock images but I'd be very interested in learning how to apply these effects with Photoshop or CSS. I have a feeling that Photoshop is a more appropriate tool.
The image I'm experimenting with is this:
It isn't the best image but for my testing purposes at least it's a similar shape and size.
I know I can use things like de-saturation or a coloured layer with a colour blend mode for this sort of thing. However, does the first image look like it has a specific effect or is it just a case of trial and error?
I appreciate this is similar to this question.
open your image in photoshop, add a new layer on top of the image, fill the layer with a color of your choice (in this case grey/black) then reduce the opacity of the layer. You will get something similar to what you want. This is a simple trick. It can be done in other ways too with more modifications.
Maybe you could get the effect by using css blur and overlaying the image with a gray layer with opacity.
You could also just create the effect in photoshop and use that
I found a way to do this with CSS3, but IE still doesn't support it. I wish to know if there is a way to do it so that it may be compatible with all of the popular browsers.
I understand I can do it with a mask, but if I want to display a user-uploaded image in the background this is not an option or at least I don't know how to achieve that. Can anyone give me an idea about it? Maybe an image processing in the background when the image is uploaded to turn it into circle and make a transparent background, but I don't know how to process that?
You can do this via CSS3 border-radius, but as you mentioned, old IE does not support this property.
But PIE.htc (PIE.js in my example) can pollyfill this in-
hence- http://codepen.io/hwg/pen/IBrow.
This uses standard border-radius, and a copy-and-pasted pie.js,
The border radius is 50% of the height and the width of the image.
I can't speak for performance (see the docs), but I think this does what you want.
You can overlay a PNG image that has a transparent circle in the middle of a square with the background color you need. Then position this over the uploaded image to give it the illusion of being a circle.
I'm looking to see if this is possible and if so how to do it. I want the user to upload an image with a white background. The image can be anything from a pair of shoes to a hat. The website will then automatically turn that white background transparent then store it. What I want to know is there a way using HTML Canvas/CSS to transform that white background to 100% transparency?
You can have a look at this answer, which explains nicely how to change colors in an image using javascript : How to change color of an image using jquery
However, you should do this using server side code, and be aware that results may vary, as just removing a color will not look nice on the edges of your object.
I'm trying to create a button, where the font is bold but it also uses a text-shadow to make the text more readable. For whatever reason the text-shadow is not appearing when its added to the CSS, though in photoshop it makes a dramatic difference using the same values.
Here's the JSFiddle
Thank you for your help
The shadow is there, but it's so faint that it's nigh impossible to perceive, especially with a relatively low alpha value and when superimposed on a background with a similar hue.
I'm going out on a limb and guessing that in Photoshop, your text shadow has a layer style that causes it to have a different effect on the underlying background color. You may need to play around with the eyedropper tool and tweak the alpha value in your text shadow, in order to achieve something that better matches your Photoshop comp.
So I need some custom colors on a layout, but I'm looking for a better way of doing it other than just slapping a giant picture with (background: url(something.jpg)) in the layout.
Mostly I'm thinking of getting a color palette (i.e. from Adobe Kuler, colourlovers, etc.), getting a 5x5 sample of each color and sticking them in an array for CSS sprites or just as separate files and accessing them through: .color-one {transparent url(./one.gif) repeat} and just reusing that whenever I'd like to use the color.
Are there any drawbacks to doing it this way? And if there are should I just stick with web-safe colors or is there a better way of doing this?
You don't need graphics to represent background colors. You are going the long way around if you use images for that. Just use colors, as graphicsdivine suggests.
Only use background images if you need to do gradients and the like. That's really where they shine.
As to your second question, no, you don't need to stick with "web-safe" colors anymore. If someone in 2010 still only can display 256 colors, well, your site won't be their biggest problem.
.color-one{background-color: #f00}
.color-two{background-color: #0f0}
You have to set the colors as background-color anyway to serve readers which don't load images. So I see no use in those images.
And remember: the smaller an image is the more has the browser to compute to calculate all positions. Repeated background images should not be smaller than 20×20px.
Why don't set background-color?
(And your suggestion wouldn't work with sprites, the renderer will also use the other parts of the image)